A MICROMANIPULATOR FOR INTRAOPERATIVE VIB RATORY HEARING TESTS WITH AN IMPLANTABLE HEARING-AID TRANSDUCER

First concepts of implantable hearing aids to be coupled to the ossicu lar chain are available for patients with combined or sensorineural he aring loss (SNHL) [9,11,12].To ensure that hearing can be improved int raoperative coupling of a test transducer to the ossicular chain is ma ndatory for allowing surgical anatomy to be checked and vibratory hear ing tests to be performed.To achieve this, the test transducer has to be held and positioned securely in situ for some minutes, avoiding ris ks for middle or inner ear structures.This is not possible using conve ntional surgical instruments.Thus,a micromanipulator to hold the test transducer during intraoperative hearing tests was developed.This surg ical device allows the surgeon safe, risk free, and controlled couplin g of the test transducer to the ossicular chain with one axial and thr ee rotational degrees of freedom.With the aid of a conventional ear re tractor (2x2 prongs),the manipulator is fixed at the patient's ear.ln conjunction with a piezoelectric test transducer, the manipulator was used in nine patients during local anesthesia.The test transducer is p art of an electronic hearing implant (Tubingen implant) specifically d esigned for SNHL that may be coupled to a middle ear ossicle or the pe rilymph of the cochlea.The micromanipulator was easy to handle.lt allo wed accurate positioning of the test transducer in the ear and the des ired coupling of the transducer's probe tip to the ossicular chain dur ing auditory tests. According to the principles of integrated safety t he intraoperative risk of ossicular or inner ear injuries caused, for instance, by the patient's head movement is minimized.The design of th e manipulator system is universal,also allowing its use for other elec tronic hearing implants or minimal invasive surgery after minor modifi cations.